Safety when using or being exposed to lasers is a very important consideration International Standards exist with regards to the classification of laser devices and the way in which different classes of laser can be used. Those laser devices that conform to the laser safety Class I definition (ie IEC825-1, AS2211) are considered the safest.
Laser emitting devices that do not fall within the Class I definition require the device and the user, and in medical applications the patient to use or be subject to one or more of the following: use of safety spectacles, interlock systems, warning lights, etc.
Laser emitting devices have a wide range of wavelength, energy and pulse characteristics and the classification system is a guide as to the way in which each device having one or more of those characteristics can be used and by whom the device can be used.
A Class I laser-emitting device can be used without restriction but in accordance with the manufacturer's instructions for the purpose for which it was designed. This means that special training and additional safety equipment is not required. Thus operating costs are less when compared to the attendant operating costs of other classes of laser-emitting devices.
A major consideration when designing laser-emitting devices is the amount of power that the source laser in the device is required to emit so as to provide adequate laser emission power from the laser device. One of the determinants of this characteristic is the required power density to be delivered at the application site over a desired area.
As the area required to be treated increases for a required power density so does the power of the source laser needed to support that requirement.
Apart from the power, pulse parameters and wavelength of the laser, another of the critical features in specifying the class of the laser is the apparent aperture of the laser source. The apparent aperture will determine the image size that the laser source can form for example on the retina of an inadvertent observer.
The requirement described above is sometimes referred to as the apparent source and it is this characteristic that is used to determine the class of the laser emitting device.
Current laser device configurations are restricted somewhat by the physics of the devices used to generate the source laser. For diode laser sources, the emitting aperture (the area of the spot beam) of the laser radiation is typically 7×1 microns for a 904 nanometer Gallium Arsenide (Ga—As) laser diode. These devices typically have pulsed outputs with 1 and 5 Watt peak powers with the pulse repetition and duration being variable to suit the application. There are many other laser diode configurations, the device type described above is an example of such devices.
In some applications it is desired to not only provide the laser radiation over a larger area but also to control the power density thus requiring an adequately high power laser source.
It is an aim of the invention described herein to provide a laser emitting device that meets not only a desired power density and spot area requirement, but that meets Class I requirements thus providing long term minimization of the running costs of the device.